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(No Model.)

J. E. WHITE CIRCUIT GLosING THERMOMETER.

No. 347,851. Patented Aug. 24, 1886.

:faillit n l 5l/@filma uw@ www UNITED STATES PATENT OEEIcE.

JOHN E. VHIIE, OF SYRAOUSE, NEV YORK.

CIRCUIT-CLOSING THERMOMETER.

SPECIFICATION forming part of Letters Patent No. 347,851,6lated August24,1886.

(No model.)

To all wtom t may concern.'

Be it known that I, JOHN E. \VIIITE, a citizen of the United States,residing at Syracuse, in the county of Onondaga and State of New York,have invented certain new and useful Improvements in Thermostats, ofwhich the following is a specification, reference being had therein tothe accompanying drawings.

This invention has relation to thermostats, and has special reference tothat class of the same which comprise a thermometric tube provided witha body of mercury and with the terminals of an electric-circuit, which,normally, are arranged separate from each other, and which are throwninto electrical connection with each other by the contact therewith of aportion of the mercury within the tube, the closing of saidconnection-that is, the completion of the circuit-being caused by anincrease of the temperature of the mercury.

rIhe object of the invention is to produce a thermostat of the classmentioned which shall be sensitive, reliable, and accurate in itsoperation, and which shall be of such construction that no corrosion orother disadvantageous action of the mercury upon the wires of thecircuit can occur by reason of the contact therewith of the mercury whennot in the act of closing the circuit.

Other objects and advantages of my invention will appear in thefollowing description, and the novel features thereof will beparticularly pointed out in the claims.

Referring to the drawings, Figure l is a front elevation, and Fig. 2 acentral vertical section, of a thermostat constructed in accordance withmy invention. Fig. 3 is a like section of a modification, and Fig. 4 isa detail in plan.

Like letters indicate like parts in all the iigures of the drawings.

A represents a tube of glass terminating at one end in an elongatedbulb, A@ and at the opposite end in an exterior annular lip, A. At thelower end of the straight portion A3 of the bore of the tube said boreis gradually expanded, preferably in a symmetrical coneshaped manner, asat A, to form the chamber A5 for the mercury B. This chamber is expandedlaterally, so that the walls thereof are comparatively thin, in orderthat the mercury contained therein may be largely exposed and sensitiveto changes in temperature. The upper end ofthe bore A of the tube isexpanded into the form of an inverted cone, A. The terminals C U-oncbeing positive and the other negative-of an electric-circuit arearranged within the cone A", and, preferably, they may rest upon theinner surface of said cone and project toward each other, though not incontact at the apex of the cone.

For the purpose of a clear illustration of the arrangement of theterminals they are shown as separated from and not inr contact with theinner surface of Ithe cone, but when arranged in contact with saidsurface they are supported and are less liable to be brought intocontact with each other by sudden jars or otherwise than when arrangedindependently of said surface, as shown.

By reason of the extremely slight diameter of the terminals C G, whichare preferably of platinum, theinsertion of the same within the cone andin duc relation to each other, is facilitated by passing them inwardlyalong the inner surface of the cone; but, as before stated, for thepurpose of illustration, they are not shown in such position.

To maintain the terminals in a desired position, I may ill a portion ofthe cone A with any desired device, material, or cement, the terminalspassing therethrough; or, I may iirst insert a cork, D, through whichthe terminals pass, and I may or may not facilitate the iusertion of theterminals through the cork by forming slits D in opposite sides thereofand then forcing the cork into the open end of the tube, thus closing ithermetically. Such closure of the tube may be further secured by theapplication of any desired cement or plastic E, which, to give furthersecurity, may be extended over, so as to embrace, cover, and include thelip A of the tube; or, as is customary in the construction of electricalglass appliances, the terminals may be inclosed or embedded in the glassof the tube itself by melting the same and compressing itinto a desiredform.

A further modification is illustrated in Fig. 3, wherein the terminals CC are passed directly through the walls of the upper cone of v the tube,the same being extended to form a placed on the tube, as shown.

erate it.

or of a series of such thermostats, arranged at' mouth, which, in thisinstance, is closed by any suitable plug and cement. This form is alsofully adapted to the method of hermetically sealing the upper end of thetube by fusing the glass and compressing it for that purpose.

F indicates the grade-mark of the thermostat. Heretofore mercurialthermostats have been constructed with one terminal of the circuitarranged at the lower end of the tube, passing through the glassthereof, and into the body of the mercury therein, and the otherterminal has been inserted above the mercury, either directly into thebore of the tube or through the walls thereof into said bore. Thisconstructionis accompanied with the constant action of the mercury uponthe terminal immersed therein, which in time corrodes the terminalfollowing the metal thereof into and Amanner the glass either becomescracked or a leak is formed and a loss of mercury results, whereby theinstrument is rendered imperfect and unreliable, as well as, intin1e,inoperative.

Now, by experiment, the quantity of mercury, the size and length of thebore, and the position of the ends of the terminals in the cone may beregulated, so that a predetermined degree of heat is rendered essentialto produce the desired operation of the mercury. For example, the tubeA, with a quantity of mercury therein, is subjected to a heat of 120,when the mercury will rise in the tube up to the point F, where anindicating-mark is The terminals are inserted in the cork so that theywill reach below the point F. The cork'is firmly seated, and each of theterminals is drawn upwardly until they coincide with the mark F, whenthey are sealed in that position. I thus produce a thermostat whichrequires 120 of heat to op- By connecting the terminals of one suitableplaces within several compartments of a building with an electricalconductor suitably arranged in said building. and connected with analarm, a rise of temperature in any of said compartments to 120 willcause said alarm tobe sounded. In this manner the thermostat is appliedfor detecting the presence of fire` or other abnormal heat.v Thiscapability of indicating a rise of temperature renders the thermostatcapable of use in many arts. For example, they may be used in detectingarise of temperature in cellars or other store-rooms for beer, where itis desired to maintain a unialso be applied to bearings of machinery,toA

indicate the heating of the journals or boxes of the same, and forindicating changes of temperature in the bodies of persons under medicaltreatment and otherwise.

I am aware that attempts have been made to utilize the expansion ofmercury to close electrical circuits in thermostats, wherein both theterminals have been conducted into the open mouth of a vessel havingmercury therein, but in such cases the' body of mercury has beendisproportionate to the object in view, in that an excessive degree ofheat was required to expand the same without diminution of the area ofits upper surface to cause it to come into contact with and connect theterminals. In my improvement I may employ a relatively-large body ofmercury, but by the cone A*,I restrict to a marked degree the area ofits upper surface to that of the relativelyslight diameter of the boreA3, whereby not vonly a less degree of heat is required to cause themercury to ascend a desired distance, but greater sensitivenes as wellas greater accu- `racy is secured in the operation of the thermostat asa whole. Furthermore, in passing the terminals freely in the open end ofthe tube, as heretofore, the action of the air, and in manufacturingestablishments, the action of gases and other chemical propertiescommingled with the air oxidizes and otherwise renders impure themercury, so that by hermetically sealing the upper end of the tube Iobviate this disadvantage. I do not, however, broadly claim hermeticallysealing the terminals in position, as this hasY been heretofore done.

I am also aware that an Sshaped mercurytube,something after the natureof a plumbers trap, has been employed, in which the bore at the upperportion has been enlarged to make room for the terminals; but themercury also IOO IIO

was to amaterial extent contained in said enlargement of the bore, whichconstruction would require an undue variation in temperature to raisethemercury to the terminals,

while in my invention the upper surface of\` the mercury is normally(that iS, at 'a degree of temperature below that at which it is desiredto close the circuit) within the reduced bore, and the terminals onlyare in the enlarged chamber or bore, thus requiring the raising, bychange of temperature, of a relative extremely small quantity of mercuryto effect a closing of the circuit; and, furthermore, it is notessential in any degree to the accomplishment of this result that theupper enlarged chamber of the bore should be in the form of an invertedcone, as any enlargement which will give room for the terminals willsuice.

I may also duplicate the circuit and terminals, if desired-'that is,have four or more, instead of two.

I have demonstrated by actual experiment and use the accuracy andscnsitiveness of the thermostat herein shown, and I attribute the sameto the peculiar form, proportion, and construction hereinbeforedescribed.

Having described my invention, what I claim isl. A thermostat comprisinga tube having a central bore terminating below in a mercurybulb andabove in an enlarged chamber in which are arranged ont of Contact witheach other the terminals of an electrical conductor, the upper surfaceof the mercury reachingnormally a point below said enlarged chamber,substantially as speeiiied.

2. A thermostat comprisi ng a tube, the lower end of the bore of whichis expanded to form a bulb, and the upper cud of which is graduallyexpanded to form an inverted eoue,in cour bination with terminalshermetieallyT arranged separately in the upper cone, from which themercury is separated by a reduced bore of the tube, substantially asspecified.

3. A thermostat comprising a tube, the bore of which is expanded to forma bulb, a grademark at a point on the tube to which the mercury thereinrises at a certain temperature, and terminals arranged in the upper endof the tube and projected to said point, substantially as specified.

4. The combination of the tube A, having the bore A, the cone shapesymmetrical enlargement thereof A", the mercury-bulb A5, and theinverted cone A", with the terminals C C, arranged within said cone A,and means for hermetieally sealing said terminalsin the tube, themercury being separated by the reduced bore from the enlargement A4,substantially as specified.

In testimony whereof I affix my signature in prese nce of two witnesses.

JOHN E. VHITE.

Vi t nesses z E. B. STocKING, XVM. S. DUvALL.

